Cosmetic coverings for prostheses are normally coloured to provide as life-like appearance as possible. One approach involves a clinician determining the appropriate colouring for a cosmetic covering by eye, e.g. by viewing the skin of the prosthesis wearer, and mixing differently coloured paints to achieve a match to the determined colours. The paint may be mixed from a palette consisting, for example, of eighty-four colours with each colour having two hundred and fifty six shades. The clinician then paints the cosmetic covering by hand. However, there is often no high degree of consistency in the colours from palette to palette. Also, clinicians will often see colours differently on account of a colour vision deficiency on the part of the clinician or on account of artificial lighting being used when the clinician is viewing the skin of the prosthesis wearer to determine the appropriate colouring. This approach typically results in 30% of painted cosmetic coverings being rejected.
Another approach involves a clinician taking colour readings with a spectrophotometer at six to ten different locations on the prosthesis wearer's skin to determine appropriate colours for a cosmetic covering. The colour values, e.g. Red, Blue, Yellow (RBY) values, for each location are determined by a computer from the spectrophotometer readings and differently coloured paints are mixed in dependence on the determined colour values.
The present inventor has appreciated shortcomings of the above known approaches.
According to a first aspect of the present invention, there is provided a method of colouring a cosmetic covering, the method comprising:                determining a calibration transform for colours of an image acquired by image acquisition apparatus;        acquiring an image of a part of a human or animal body with the image acquisition apparatus to provide a digital colour image;        transforming the digital colour image with the calibration transform to provide a colour compensated digital colour image        conveying at least one colour characteristic of at least one colour within the colour compensated digital colour image to a pigment mixing apparatus, which is operative to mix a plurality of pigments of different colours in dependence on the at least one colour characteristic to produce at least one mixed pigment; and        applying the at least one mixed pigment to a cosmetic covering.        
In use, an image of a part of a human or animal body, such as the left hand of person who wears a prosthetic right hand, is acquired with the image acquisition apparatus to provide a digital colour image of the part. The digital colour image may be a two dimensional digital colour image. The digital colour image may stored as a two dimensional digital array. Thus and in contrast to the known approach using the spectrophotometer, a digital colour image is obtained rather than a number, e.g. six to ten, colour readings from the human or animal body part. The colours represented in the digital colour image are liable to differ from the true colour values of the human or animal body part on account of the characteristics of the image acquisition apparatus or the lighting when the image is acquired. Hence, the steps of determining the calibration transform for the image acquisition apparatus and transforming the digital colour image with the calibration transform to provide a colour compensated digital colour image compensates for inaccuracies of the image acquisition apparatus in representing colours.
The cosmetic covering may be configured to cover a prosthesis, such as a hand prosthesis, or foot prosthesis, for example. More specifically, the cosmetic covering may be a surface of the cosmetic covering. In one form, the at least one mixed pigments may be applied by a person, e.g. using a brush. In another form, the at least one mixed pigments may be applied by pigment applying apparatus, such as spray painting apparatus.
More specifically, the method further comprises: acquiring an image of a colour chart with the image acquisition apparatus to provide a colour chart image; and determining the calibration transform in dependence on the colour chart image and colour values represented in the colour chart. The present step may be carried out under substantially the same conditions, e.g. in terms of at least one of lighting and image acquisition apparatus configuration, as the step of acquiring the image of the body part. More specifically, the colour chart may comprise a plurality of areas, with each area containing a different colour, e.g. according to a standard. Thus, the colour chart may be a Gretag MacBeth colour chart.
Alternatively or in addition, the calibration transformation may comprise a transformation for each of Red, Green and Blue values. The calibration transformation may have the form of a Look Up Table (LUT) for each of Red, Green and Blue. A LUT may have been determined by sparsely populating the LUT with differences between image colour values and actual colour values. A LUT may be populated by interpolation between sparse values contained in the LUT. Values in a LUT may be filtered. The LUT values may be filtered by at least one of: a point fitting curve, such as a Catmull-ROM point fitting curve; and a rolling average filter, such as a rolling average filter with twelve taps.
Alternatively or in addition, the method may comprise acquiring a plurality of different images of the part of the human or animal body. For example, where the part is a hand, an image of the top of the hand, an image of the bottom (i.e. palm side) of the hand and an image of the thumb side of the hand may be acquired. Hence, each of the plurality of acquired digital colour images may be transformed by the calibration transform.
Alternatively or in addition, the method may further comprise disposing the part of the human or animal body in relation to the image acquisition apparatus and displaying an image of the part acquired by the image acquisition apparatus on display apparatus, such as on a Visual Display Unit (VDU). The present step may be carried out before the step of acquiring an image of the part to provide the digital colour image. Hence, the present step may be used to determine whether or not the part is properly disposed in relation to the image acquisition apparatus and, if not, the part may be moved or its orientation changed to achieve proper disposition.
Alternatively or in addition, the method may comprise receiving the body part in an enclosed space.
More specifically, the enclosed space may be illuminated in a controlled fashion by means of a light source. Alternatively or in addition, the enclosed space may be illuminated by a light source configured to provide for substantially uniform illumination in a plane, e.g. a plane extending generally perpendicular to a path between the image acquisition apparatus and the part of the human or animal body.
Alternatively or in addition, the enclosed space may be illuminated by a light source configured to be disposed proximate the image acquisition apparatus. More specifically, the light source may be configured to receive a lens of the image acquisition apparatus such a light emitting part of the light source is disposed around the lens. Alternatively or in addition, the light source may comprise a light emitting part of annular form. The light emitting part may comprise a plurality of Light Emitting Diodes (LEDs) disposed in relation to each other in a generally square pattern.
Alternatively or in addition, the data acquisition apparatus may comprise a digital camera. More specifically, the digital camera may be a true colour digital camera. The true colour nature of the digital camera may be afforded by a characteristic of an optical lens disposed between the part of the human or animal body and an aperture of the digital camera.
Alternatively or in addition, the apparatus may be configured to control the camera in respect of at least one of: at least one RGB analogue gain; at least one of HSV values corresponding to RGB values; exposure time; a gain of the camera; gamma; white balance; light power; contrast; and saturation.
Alternatively or in addition, the method may further comprise: displaying the compensated digital colour image on display apparatus; and selecting a plurality of different areas on the compensated digital colour image. The plurality of different areas may be selected by an operator, e.g. by means of pointing at each area with a mouse and clicking.
More specifically, colour characteristics of the colours within the plurality of different selected areas may be conveyed to the pigment mixing apparatus, which is operative to mix a plurality of pigments of different colours in dependence on the colour characteristics to produce a plurality of mixed pigments. The colour characteristics may be Red, Blue and Yellow (RBY) values determined from the plurality of different selected areas, e.g. by means of processing apparatus. The plurality of mixed pigments may correspond respectively to colours within the plurality of different selected areas. At least one of the pigments may be paint.
Alternatively or in addition, the pigment mixing apparatus may comprise a plurality of pigment dispensers, each pigment dispenser containing a pigment of a different colour.
Different batches of pigment of a particular colour may be of a slightly different colour. Hence, it may be desired to provide for colour consistency from batch to batch. Therefore, alternatively or in addition, the method may further comprise determining a colour of a batch of pigment, e.g. a fresh batch, by means of colour determining apparatus. The colour determining apparatus may comprise apparatus, such as a spectrophotometer, that is operative to determine a bulk colour value (e.g. at a measurement location) for the pigment batch. The colour determining apparatus may be operative to determine the Red, Blue, Yellow (RBY) values of the pigment.
More specifically, the method may further comprise comparing the determined colour of the pigment with a predetermined colour, e.g. as determined by measuring the colour of another batch of pigment, such as the batch most recently present in the colour mixing apparatus.
Alternatively or in addition, the method may further comprise changing proportions of pigments of different colours used to produce a pigment mixture in dependence on the determined colour of the batch of pigment. Hence, for example, relative amounts of Red Blue and Yellow pigments used to form the plurality of mixed pigments may be changed to take account of a change in colour from one batch of pigments to another.
Alternatively or in addition, the method may further comprise: conveying the colour compensated digital colour image to printing apparatus; and printing the colour compensated digital colour image by means of the printing apparatus. The colour compensated digital colour image may be wirelessly conveyed to the printing apparatus.
More specifically, the method may further comprise acquiring by image acquisition apparatus an image of an image printed by the printing apparatus to provide a digital colour printed image. The image acquisition apparatus may comprise a digital camera. Preferably, a calibration transform may have been determined for the image acquisition apparatus. Hence, any contrary effect as regards colour caused by the image acquisition apparatus and/or lighting when the image acquisition apparatus is operative may be minimised. The printed image may comprise a colour chart, e.g. a colour chart stored in processing apparatus. The digital colour printed image, e.g. of the colour chart, may be conveyed to processing apparatus.
Alternatively or in addition, the method may comprise: determining a printer calibration transform for colours of an image, e.g. of a colour chart, printed by the printer; and transforming a colour compensated digital colour image in dependence on the printer calibration transform. Thus, the printer may print an image that properly reflects the true colours of the colour compensated digital colour image.
According to a second aspect of the present invention, there is provided apparatus for colouring a cosmetic covering, the apparatus comprising:                image acquisition apparatus operative to acquire an image of a part of a human or animal body to provide a digital colour image;        processing apparatus operative to determine a calibration transform for colours of an image acquired by the image acquisition apparatus,        the processing apparatus being further operative to transform the digital colour image with the calibration transform to provide a colour compensated digital colour image;        pigment mixing apparatus operative to mix a plurality of pigments of different colours in dependence on at least one colour characteristic of at least one colour within the colour compensated digital colour image to produce at least one mixed pigment; and        pigment applying apparatus operative to apply the at least one mixed pigment to a cosmetic covering.        
The cosmetic covering may be configured to cover a prosthesis, such as a hand prosthesis. More specifically, the cosmetic covering may be a surface of the cosmetic covering. In one form, the at least one mixed pigments may be applied by a person, e.g. using a brush. In another form, the at least one mixed pigments may be applied by pigment applying apparatus, such as spray painting apparatus.
More specifically, the processing apparatus may comprise a computer, such as a Personal Computer (PC). The image acquisition apparatus may comprise a colour digital camera and may be configured to convey the digital colour image to the processing apparatus for processing thereon.
According to a third aspect of the present invention, there is provided a method of determining skin colour, the method comprising:                determining a calibration transform for colours of an image acquired by image acquisition apparatus;        acquiring an image of a part of a human or animal body with the image acquisition apparatus to provide a digital colour image; and        transforming the digital colour image with the calibration transform to provide a colour compensated digital colour image.        
Alternatively or in addition, the method may further comprise: displaying the compensated digital colour image on display apparatus; and selecting a plurality of different areas on the compensated digital colour image. The plurality of different areas may be selected by an operator, e.g. by means of pointing at each area with a mouse and clicking.
More specifically, colour characteristics of the colours within the plurality of different selected areas may be conveyed to the pigment mixing apparatus, which is operative to mix a plurality of pigments of different colours in dependence on the colour characteristics to produce a plurality of mixed pigments. The colour characteristics may be Red, Blue and Yellow (RBY) values determined from the plurality of different selected areas, e.g. by means of processing apparatus. The plurality of mixed pigments may correspond respectively to colours within the plurality of different selected areas. At least one of the pigments may be paint.
Alternatively or in addition, the method may further comprise applying the plurality of mixed pigments to a person. Thus, the method of the present invention may be used for applying make-up or for cosmetic tanning. Alternatively, the method of the present invention may be used for applying mixed pigments for cosmetic skin repair, e.g. for persons with burn scarred skin.
According to a fourth aspect of the present invention, there is provided apparatus for determining skin colour, the apparatus comprising:                image acquisition apparatus operative to acquire an image of a part of a human or animal body to provide a digital colour image; and        processing apparatus operative to determine a calibration transform for colours of an image acquired by the image acquisition apparatus,        the processing apparatus being further operative to transform the digital colour image with the calibration transform to provide a colour compensated digital colour image.        
More specifically, the processing apparatus may comprise a computer, such as a Personal Computer (PC). The image acquisition apparatus may comprise a colour digital camera and may be configured to convey the digital colour image to the processing apparatus for processing thereon.
Further embodiments of the second aspect of the present invention may comprise one or more features of the first aspect of the present invention.